custom axhaust

Should I go with 2.75 or 3" for the exhaust? I dont want to lose any power, but I also want it to be able to support turbos if I plan on going that route some time in the future. I found a web sight of a guy who had an SL and put flowmasters 50 series on it and 3" custom exhaust and it sounded like a beast. I'm just not shure on the size of the piping to go. Also can you give me an estimate of how much it might cost?
Thanks

well 2.5 is good for n/a but I if you're planning to eventually turbo, than I'd say go for 2.75 (that's what the stock VR4's exhaust is)...

2.5 you wont back pressure to make power

from what I discussed with Musashi, flow master mufflers seem to create back pressure, so that could be a reason as to why it worked with the 3" exhaust... musashi, any thoughts?